Synthesis and characterization of bridged bis(amidato) rare earth metal amides and their applications in C–N bond formation reactions

Abstract

Based on three bisamide proligands H₂Lⁿ (n = 1–3) (H₂L¹ = [(Me₃C₆H₂CONHCH₂)₂CH₂], H₂L² = [(Me₃C₆H₂CONHCH₂)₂C(CH₃)₂], H₂L³ = [Me₃C₆H₂CONH(CH₂)₂]₂NCH₃), eight bis(amidato) trivalent rare-earth metal amides {LⁿRE[N(TMS)₂]}₂ (n = 1, RE = La (1), Sm (2), Nd (3), Y (4); n = 2, RE = La (5), Nd (6); n = 3, RE = La (7), Nd (8); TMS = SiMe₃) were successfully synthesized by treatment of H₂Lⁿ with RE[N(TMS)₂]₃ in a 1 : 1 molar ratio. Complexes 3, and 5–8 were characterized by single-crystal X-ray diffraction, and NMR characterization was carried out for the La complexes 1, 5, 7 and the Y complex 4. These complexes exhibited high catalytic activities in both the direct amidation of aldehydes and the addition of amines with carbodiimine. It was found that the bis(amidato) rare earth metal amides bearing different linkers have different effects on the transformations and lanthanum and neodymium complexes performed better than others.